The main difference between peripheral nerve and spinal nerve is that peripheral nerves reside outside the central nervous system, whereas spinal nerves reside within the central nervous system.
Nerves are glistening white chord-like bundles of fibers surrounded by a sheet that connects the nervous system with the other parts of the body. They are a part of the nervous system. However, there are different types of nerves, including peripheral nerves, spinal nerves, and cranial nerves. Both peripheral nerves and spinal nerves are responsible for transmitting signals throughout the body. However, there are several differences between peripheral nerve and spinal nerve.
Key Areas Covered
1. What are Peripheral Nerves
– Definition, Structure, Function
2. What are Spinal Nerves
– Definition, Structure, Function
3. Difference Between Peripheral Nerve and Spinal Nerve
– Comparison of Key Differences
Key Terms
Peripheral Nerve, Spinal Nerve
What are Peripheral Nerves
Peripheral nerves are nerves that reside outside the brain and spinal cord. These nerves belong to the peripheral nervous system. Moreover, the peripheral nervous system has two main parts: the autonomic nervous system and the somatic nervous system.
The main unit of the peripheral nervous system is the axon. Peripheral nerves have both myelinated and unmyelinated axons. A myelinated fiber occurs when a single Schwann cell surrounds a single axon, creating a myelin sheath, whereas unmyelinated fibers form when a single Schwann cell surrounds multiple axons. Moreover, layers of Schwann cells form the myelin sheaths. Additionally, peripheral nerves carry either efferent (motor) or afferent (sensory) electrical impulses.
There are three connective tissue sheaths in large peripheral nerves. They support and protect axons and myelin sheaths. Endonureum is the innermost sheath out of them, associated with each individual myelinated axon. A sheath of the perineum covers the Swan cells, endoneurial sheaths, and axons. Mrerinureum protects the content inside from infections and toxins. The epineurium, being the third layer, covers the whole peripheral nerve. It protects the axon against the stretching forces on the nerve.
Nerve fascicles are the smallest units of nerves. Between fascicles exists fat in different amounts. Moreover, the lower parts contain more fat than the upper parts. Each fascicle has motor, sensory, and sympathetic fibers. There are about 10 fascicles in large peripheral nerves.
Peripheral nerves send messages from the brain and spinal cord to the other parts of the body. Peripheral nerves are fragile. Therefore, they are more likely to get damaged. We call damage to a peripheral nerve peripheral neuropathy. A nerve injury impairs the ability of the brain to communicate with the other parts, muscles, and organs. Injuries from accidents, autoimmune diseases such as rheumatoid arthritis and lupus, and certain medical conditions cause peripheral neuropathy.
What are Spinal Nerves
Spinal nerves are mixed nerves that directly interact with the spinal cord to modulate motor and sensory information from the body’s periphery. They also carry autonomic signals. They are bundles of nerve fibers that connect to the spinal cord and carry information to and away from the spinal nerves.
Spinal nervous supply is present all over the body except in the head and neck regions. These spinal nerves belong to the peripheral nervous system. Moreover, spinal nerves help control the body parts in association with the brain’s higher centers. In fact, humans have 31 pairs of spinal nerves. Each of them is associated with a segment in the vertebral column. Generally, they consist of eight cervical spinal nerve pairs, twelve thoracic pairs, five lumbar pairs, five sacral pairs, and one coccygeal pair. Each spinal nerve also has a mix of nerve fibers from the dorsal and ventral roots of the spinal cord.
However, if a spinal nerve is cut, damaged, or injured, the region of the body that it supplies can become disconnected from the central nervous system’s control. Therefore, such damage can cause pain, weakened function, loss of sensation, and even death.
Difference Between Peripheral Nerve and Spinal Nerve
Definition
Peripheral nerves are nerves that reside outside the brain and spinal cord, whereas spinal nerves are mixed nerves that directly interact with the spinal cord to modulate motor and sensory information from the body’s periphery.
Location
Peripheral nerves are outside the central nervous system, whereas spinal nerves are within the central nervous system.
Structure
Moreover, peripheral nerve fibers are made up of bundles of nerve fibers or axons that are surrounded by a protective sheath called epineurium. Spinal nerves, on the contrary, are protected by a bony vertebral column and organized into 31 pairs that form branches and go to different body parts.
Transmission of Information
Peripheral nerve fibers are classified based on their function, such as sensory nerves that transmit information from the body to the brain and motor nerves that control movement and other functions. Spinal nerves are made up of both sensory and motor fibers and are classified based on the region of the spinal cord from which they originate.
Conclusion
Nerves are a part of the nervous system. Moreover, there are different types of nerves according to their structure and function, and peripheral nerves and spinal nerves are parts of the nervous system. The main difference between peripheral nerve and spinal nerve is that peripheral nerves are located outside the central nervous system, whereas spinal nerves are located within the central nervous system.
Reference:
1. “Spinal Nerves.” Psychopedia.
2. “Peripheral Nervous System (PNS).” Cleaveland Clinic.
Image Courtesy:
1. “Central Nervous System – Peripheral Nervous System schematic” By David Nascari and Alan Sved – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “1321 Spinal Nerve Plexuses” By OpenStax – (CC BY 4.0) via Commons Wikimedia
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